silicon and trichlorosilane

A second-generation polyphenylene dendrimer 1 is shown to self-assemble into nanofibers. To guide the formation of the dendrimer fibers into well-defined patterns, 1H,1H,2H,2H-perfluorodecyltrichlorosilane is grafted in the gas phase onto a silicon substrate. De-wetting of the solution on the nanopatterned surface results in the formation of a nanostructured template, into which fiber growth subsequently occurs under the constraints set by the de-wetted morphology.

Topics: Dendrimers; Furans; Gases; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Nanostructures; Polymers; Silanes; Silicon

Electronic structures at the Si/SiO2/molecule interfaces were studied by Kelvin probe techniques (contact potential difference) and compared to theoretical values derived by the Helmholtz equation. Two parameters influencing the electronic properties of n-type <100> Si/SiO2 substrates were systematically tuned: the molecular dipole of coupling agent molecules comprising the layer and the surface coverage of the chromophoric layer. The first parameter was checked using direct covalent grafting of a series of trichlorosilane-containing coupling agent molecules with various end groups causing a different dipole with the same surface number density. It was found that the change in band bending (DeltaBB) clearly indicated a major effect of passivation due to two-dimensional polysiloxane network formation, with minor differences resulting from the differences in the end groups' capacity to act as "electron traps". The change in electron affinity (DeltaEA) parameter increased upon increasing the dipole of the end group comprising the monolayer, resulting in a range of 600 mV. Moreover, a shielding effect of the aromatic spacer compared with the aliphatic spacer was found and estimated to be about 200 mV. The density effect was examined using the 4-[4-(N,N-dimethylamino phenyl)azo]pyridinium halide chromophore which has a calculated dipole of more than 10 D. It was clearly shown that upon increasing surface chromophoric coverage an increase in the electronic effects on the Si substrate was observed. However, a major consequence of depolarization was also detected while comparing the experimental and calculated values.

Topics: Electrons; Membranes, Artificial; Molecular Structure; Silanes; Silicon; Silicon Dioxide; Surface Properties

Using low-pressure chemical vapor deposition of silicon dioxide, we have reduced the size of 56-nm features in a silicon nitride membrane, called a stencil, down to 36 nm. Sub-50-nm uniformly sized nanoparticles are fabricated by electron-beam deposition of Pt through the stencil mask. A self-assembled monolayer (SAM) of tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane was used to reduce Pt clogging of the nanosize holes during deposition as well as to protect the stencil during the postdeposition Pt removal. X-ray photoelectron spectroscopy shows that the SAM protects the stencil efficiently during this postdeposition removal of Pt.

Topics: Electrons; Microscopy, Electron, Scanning; Molecular Conformation; Nanotechnology; Nitrogen; Platinum; Silanes; Silicon; Silicon Dioxide; Spectrometry, X-Ray Emission; Spectrophotometry, Infrared

The reactive airway dysfunction syndrome (RADS) is a recently described syndrome in which bronchial hyperreactivity and asthmatic symptoms develop in previously healthy individuals after a single large exposure to an irritating gas, fume, or vapor. We report a cluster of three Philadelphia police officers who developed RADS after a common exposure to toxic fumes from a roadside truck accident. Results of initial pulmonary function testing were normal in all three, and methacholine challenge was required for diagnosis in two out of the three. This syndrome needs to be recognized by physicians dealing with environmental or industrial medicine as a potential cause of loss of work or inability to perform on the job. Also, there is a potential for multiple individuals to develop this syndrome from a single incident.

Topics: Accidents, Traffic; Adult; Asthma; Bronchial Provocation Tests; Chlorides; Forced Expiratory Volume; Humans; Male; Middle Aged; Silanes; Silicon; Silicon Compounds; Sodium Hydroxide; Vital Capacity